class F1(object):
    def show(self):
        print ('F1.show')

class S1(F1):
    def show(self):
        print ('S1.show')

class S2(F1):
    def show(self):
        print ('S2.show')

def Func(obj):
    print (obj.show())

s1_obj = S1()
Func(s1_obj) 

s2_obj = S2()
Func(s2_obj)